Sorry folks - I've broken it. I ran an optimisation tool after the update, and I'm afraid it toppled the server over. Oh the calamity! :S I've put in a request to reboot it, and will run the optimisation from our server instead once we're back up, then recount and rebuild everything.
Bear with me while I resolve it :)
The server is back up - running a repair/optimisation of the main tables, and then I'll try again :)
EDIT: The problem was caused by a few of the new files I uploaded getting corrupted on their way - we'll blame BT for that - and resulting in a forum that worked, but only just. All the fancy stuff like dynamic pages, fly-out menus and such were broken until we re-uploaded the file set, and after a hard-refresh of your browser things should now be normal. :)
To Hard Refresh your Browser
To speed browsing, Browsers cache commonly used files, which reduces the download on a page that shares files and code with other pages you have been viewing. That's cool until the page is updated to clear a bug or similar, when a hard-refresh of everything on the page becomes necessary. To do that, Press CTRL+F5 in Firefox & IE, CTRL+SHIFT+R in Chrome, and Opt+Cmd+E for Safari in Mac